The present invention relates to a method and apparatus for making a plastic sleeve, and particularly relates to a method of manufacturing a boot seal for sealing a movable joint in a vehicle steering or suspension system.
A conventional rack and pinion steering gear for a vehicle has a boot seal. The boot seal protects a ball joint that connects the rack to a tie rod and a bearing that allows movement between the rack and a housing. If the boot seal is damaged during operation of the vehicle, water and other contaminants may contact the ball joint and the rack and cause the ball joint and the rack to rust and bind against movement. Damage to the boot seal can be caused by fatigue, punctures, cuts, tears, or abrasive wear.
A boot seal is typically formed by molding a thermoplastic or a thermosetting elastomer into the configuration in which the boot seal is to be installed in the rack and pinion steering gear apparatus. The molded boot seal is placed around the tie rod and the housing and secured by metal clips.
The present invention is a process for making a corrugated plastic sleeve having an internal diameter, a circumferential rib projecting inward from the internal diameter at one end of the sleeve, and an external first groove aligned with the rib. The rib is for securing the plastic sleeve to a member. The process comprises feeding a plastic into an extruder die. The plastic is extruded from the extruder die as a molten plastic stream into a mold cavity having an inner wall with dimensions greater than the outside dimensions of the molten plastic stream. The inner wall of the mold cavity includes an end portion and a corrugated portion. The end portion includes a projection extending radially inward of the mold cavity and circumferentially completely around the mold cavity. The molten plastic stream is vacuum expanded radially against the mold cavity inner wall and around the projection. Thus, a plastic sleeve with the circumferential rib and the aligned external first groove at one end of the plastic sleeve is formed.
The present invention also relates to an apparatus for making a plastic sleeve having an internal diameter, a circumferential rib projecting inwardly from the internal diameter at one end of the sleeve, and an external first groove aligned with the rib, wherein the rib is for securing the plastic sleeve to a member having a second external groove for receiving the rib. The apparatus comprises an extruder die for extruding a molten plastic stream and a mold cavity for receiving the molten plastic stream from the extruder die. The mold cavity has an inner wall with dimensions greater than the outside dimensions of the molten plastic stream. One end of the inner wall includes a projection extending radially inward of the mold cavity and circumferentially completely around the mold cavity. The apparatus further comprises a vacuum system for expanding the molten plastic stream radially against the mold cavity and around the projection. Thus, a plastic sleeve with the circumferential rib and the aligned external first groove at one end of the sleeve is formed.